Hybrid vehicles having an engine for driving travel of the vehicle and a motor for driving travel of the vehicle are widely used. A hybrid vehicle travels by means of a driving force of at least one of an engine and a motor. As energy efficiencies of an engine and a motor vary depending on rotating states thereof, energy efficiencies can be improved by controlling contributions of the engine and the motor to the travel driving force according to traveling states of the vehicle.
A hybrid vehicle has a generator which charges a battery for supplying electrical power to a motor using electrical power generated by the driving force of the engine. The generator charges the battery during the time that the engine is driven, and stores electrical energy for driving the motor in the battery. Thereby, the hybrid vehicle can travel with a supply of gasoline for driving the engine, without having to charge the battery from the outside.
In recent years, an increasing number of users prefer operability and ride quality of a hybrid vehicle traveling by the driving force of the motor. Also, a demand to reduce engine exhaust gas has increased.
As such, an electric/hybrid vehicle which travels not only in an HV mode, in which contributions to the travel driving forces of the engine and the motor are controlled depending on traveling states of the vehicle, but also in an EV mode, in which the vehicle travels solely by the driving force of the motor, has been developed. Generally, an electric/hybrid vehicle is adapted such that those traveling modes can be set in accordance with choices of the user.
When a vehicle travels in the EV mode, as the battery will never be charged with electrical power generated by the driving force of the engine, the charged electrical energy of the battery may be insufficient. As such, in the electric/hybrid vehicle, when the charged electrical energy becomes insufficient, the mode is forcibly set to the HV mode even when the EV mode has been selected. Further, in order to prevent shortage of the charged electrical energy, an externally chargeable electric/hybrid vehicle, having an external charging device for charging the battery from a power source such as a commercial electrical output, has been invented.
PATENT DOCUMENT 1: JP 9-98517 A
PATENT DOCUMENT 2: JP 2002-274219 A